Apple announced watchOS 4 at its WWDC event in June, and showed off a variety of new features that it will bring to Apple Watches. One of the new features is called GymKit, which lets you sync your Apple Watch's Workout app with a treadmill or other piece of gym equipment, using its NFC chip - and in this tutorial we explain how this works.

Just to stress, however: this is how you'll use the feature, but not for a month or two. watchOS 4 is available in beta at present, but only for developers - there is no public beta of watchOS 4 - and won't be rolled out to the general public until the autumn. And even if you're one of the small number of people with watchOS 4 ahead of the launch, the compatible equipment won't start appearing in gyms for some time. Read next: How to lose weight with an Apple Watch

What is GymKit?

GymKit, which Apple calls "a groundbreaking technology platform to connect workouts with cardio equipment", is one of Apple's latest APIs, announced along with ARKit at WWDC. (APIs are frameworks that Apple and other companies make available to app developers and which make it easier for them to build in features, or compatibility with certain features, added to a central platform.) GymKit, as the name suggests, focuses on making Apple devices work seamlessly with gym equipment.

In a press release, Apple said: "With GymKit, customers using their favourite cardio equipment will soon be able to pair their Apple Watch directly to treadmills, ellipticals, indoor bikes or stair steppers from global manufacturers such as Life Fitness and Technogym with a simple tap.

"In an industry first, data not previously communicated between smartwatch and fitness machine will sync seamlessly - including calories, distance, speed, floors climbed, incline and pace - resulting in the most accurate measurements possible with less device management." Read next: How to use the Apple Watch Workout app

How to sync Apple Watch with a treadmill

Make sure you've got watchOS 4

The first step is to make sure your Apple Watch is set up with watchOS 4 or later - any earlier version of watchOS won't be able to sync with gym equipment.

Here's how to update watchOS on your Apple Watch.

Is the treadmill compatible with watchOS?

It isn't enough that your Apple Watch is equipped with watchOS 4; the treadmill also needs to be compatible with GymKit, and it will be a while before this is widespread.

In theory this is where the beta testing period will come in handy: developers get an early sighter of the new software ahead of the general public and can start working on compatible systems. So it's possible that compatible machines will be available in time for or shortly after watchOS 4's launch.

As usual Apple has been able to use its clout to good effect, and a lot of the major gym equipment manufacturers, including Cybex, SCIFIT, Star Trac, Nautilus, LifeFitness, StairMaster and Schwinn, have announced that they're on board with the scheme. But treadmills are expensive and we suspect that most gyms will be reluctant to replace them without good reason; even though the Apple Watch is undoubtedly the most successful smartwatch out there, it's still a niche product with a comparatively small installed base.

On the other hand, if a gym has gone to the expense of replacing a treadmill with a new GymKit-compatible model, it's sure to trumpet this - so look out for a GymKit label or other sign that it can be synced with an Apple Watch. Read next: How to get every Activity achievement badge on Apple Watch

How to sync Apple Watch with treadmill: watchOS 4

Pair your watch and start a workout

First of all you need to set up a a connection between your watch and the gym equipment. Assuming the treadmill is compatible it will have been equipped with an NFC reader, so you will just have to tap your Apple Watch against this to pair the two devices. Start a workout, and the data entered into your watch will come direct from the treadmill.